The linked site may help. Link

If you are new to piping, start your career off on the right foot. That would mean that you will rarely if ever use thrust blocks. The reasons for not using thrust blocks are explained here:

Link

Thrust blocks were generally used on unrestrained connections (bell and spigot) for underground work. Most piping is now restrained in some manner using restraints such as megalugs.

Thrust blocks have fallen out of favor because thrust block design is based on unknown characteristics of soils.

The preferred thrust restraint will be mechanical restrained joints. You should forget the thrust blocks and use these restrained pipe joints. Restrained pipe joint design will be simpler and the end results are more reliable as you do not know the soil conditions or the method that Contractor will use to install the thrust blocks. Most Contractors don't install thrust blocks properly, they typically just throw a bag of cement behind the elbow.

Thrust Block Design

Thank you for the response.
It is a requirement to install concrete thrust blocks by Engineers and SUDAS.
I am still looking for an answer on how much CY would you calculate for each bend? is there a formula?

Thanks again.

Well then, put mechanical joints on as well as a thrust block. The link above titled "Thrust Block Design" has the information.

I don't trust thrust blocks either - dig in accidents are all too common.
Fred